The Florida judge presiding over George Zimmerman's murder trial reversed herself today and announced that the jurors will be sequestered for the trial.

"The parties have, both sides have, stipulated that this trial will last between two and four weeks," Judge Debra Nelson said. "Based upon that approximate stipulation, I will be sequestering the jury."

Earlier the judge had ruled that the six-member jury and four alternates would be anonymous, but declined to have them sequestered.

In February 2012, Zimmerman, a neighborhood watchman in Sanford, Fla., shot and killed 17-year-old Trayvon Martin after a confrontation in the dark. Zimmerman has said he shot the black teen, who he said had been acting "suspiciously," in self-defense.

The racially charged case has attracted national attention.

Jurors are rarely sequestered, isolated by the court away from their families and their homes, for a second degree murder trial. But suspicious testimony by potential jurors this week has triggered fear of a tainted jury pool.

On Wednesday, a potential juror assigned the number E7 told the court he had little knowledge about the case. However on an earlier Facebook posting months ago the juror appeared to have written "I CAN tell you THIS. Justice…IS coming."

An ABC News search of the Facebook page revealed that a person resembling E7 wrote on March 21, 2012 -- the same date as on the court record -- an inflammatory comment in response to a posting about the case touting the site www.justicefortrayvonmartin.com. The posting also alleged a conspiracy involving Zimmerman and local police.

The potential juror was asked in court what he knew about the Zimmerman case beyond what was listed on the questionnaire,

"Hmm. To be strictly honest, it's hard to remember," the potential juror responded. He was then directly asked if he had used Facebook to post about the case and he responded "Nope."

Moments later, both counsels approached the bench, and the judge asked him about a Facebook post, and he confirmed it was his.

Lawyers from both sides today were confronted with outright bias by potential jurors.

"Your opinion that you formed, what was it?" prosecutor Bernie de la Rionda asked one candidate.

"That George Zimmerman should go home," responded juror E-81.

In four days of jury selection at least 24 jurors are in the potential jury pool and 85 have been dismissed. Lawyers on both sides are trying to find 40 potential jurors before they begin a more intense question-and-answer session known as voire dire.

Both sides are wary of potential "moles," individuals who say they know little about the case that made national headlines because they are eager to be picked.

"The stealth juror is one that says the answers that everyone wants to hear but inside has a secret, hidden agenda," said veteran defense attorney Mark Eiglarsh, a legal analyst.

Legal analysts say Nelson's decision to sequester the jury could be to protect them from outside influence.